The fuel tank system of a long-range commercial airliner often contains a main fuel tank located in each of the wings of the aircraft and a center fuel tank located between the main wing tanks. Each of these fuel tanks typically requires independent fuel systems, including redundant fuel pumps, fuel level sensors, temperature probes, and plumbing for refueling, venting, cross-feeds, and tank-to-tank transfers. Because the center fuel tank normally lies within the 15-degree rotor-bust zone of a wing-mounted engine, it is subject to damage and/or penetration in an uncontained engine failure. Consequently, the fuel in the center fuel tank is normally utilized first during operation to preserve the fuel in the main wing tanks for use for an emergency diversion to an airport in the event of such a failure.
Modifications of an aircraft design are often made to allow the aircraft to efficiently fulfill different roles. For example, a derivative of a commercial airliner may be designed to carry a lighter load on shorter routes than the base design. To accommodate these needs, the fuselage of the airliner may be shortened, accommodating fewer passengers, and the center fuel tank removed. Removing the center fuel tank saves weight from the reduction in overall fuel load as well as the removal of the fuel systems and structures associated with the center fuel tank.
However, it is still desirable to give the derivative aircraft design the greatest fuel capacity possible without adding excessive cost or weight. One solution is to add auxiliary fuel tanks in other areas of the aircraft, such as the fuselage or tail. However, this requires complete fuel systems to be added to the design to support the additional tanks, adding to cost, weight, and complexity as well as potentially requiring substantial modification of the structure of the aircraft. Another alternative involves structurally modifying the main wing tanks and associated fuel systems to extend each of the main wing tanks inboard into the areas previously occupied by the center tank. However, doing so may place the main wing tanks into the 15-degree rotor-bust zone, which is unacceptable for the safety reasons mentioned above.
Moreover, extending the main wing tanks in this fashion may be a costly and complex design modification. It is essential that certain components of the fuel system remain covered with fuel during operation of the aircraft, such as fuel pickups and hydraulic system heat-exchangers. Accordingly, these components must be located at the lowest point of the main wing tank. If the main wing tank is extended inboard on the aircraft, these components often must be relocated to the new low point of the extended tank. This may require the main wing tank fuel systems and plumbing to be redesigned, or may not be feasible at all because of the confined space of the extended portion of the tank.
It is with respect to these considerations and others that the disclosure made herein is presented.